Secondary balancer of vertical engine of outboard motor

Abstract

A secondary balancer is used for an outboard motor vertical in-line engine which includes a crankcase, a cylinder block and a cylinder head, which are arranged in this order from a front side of the engine (i.e., hull side of an outboard motor), a crankshaft placed in the engine in a substantially vertical direction, an intake pipe placed on one side of the engine, a throttle body and an intake silencer which are disposed on a front side of the crankcase, and a balancing device including a primary balancer and a second balancer. The secondary balancer includes a pair of balancer shafts disposed in a space formed between the crankcase and the intake silencer.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates a secondary balancing device (balancer) of an outboard motor vertical type engine and the engine provided with such a secondary balancer.2. The Related ArtA four-stroke-cycle engine is susceptible to vibration, which is caused by a reciprocating motion of a piston of a cylinder assembly of the engine. For the purpose of eliminating the vibration, a certain type of engine is provided with a balancer or balancing device (called “balancer” hereinlater). Such a balancer includes a balancer shaft with a balancer weight corresponding to the total mass of movable parts such as piston and connection rod of the engine so that rotation of the balancer shaft in conjunction with operation of the engine eliminates the vibration caused by the operation of the engine.The above-mentioned balancer may include a primary balancer, to eliminate primary vibration, in which a vibration exciting force generates once during o...

AI Technical Summary

Benefits of technology

An object of the present invention, which was made in view of the above-mentioned circumstances, is therefore to provide a secondary balancer of an outboard motor engine, which permits to achieve miniaturization and enables existing structural parts to be used as they are, and also provide an outboard motor-vertical in-line engine provided with such a secondary balancer.

This and other objects can be achieved according to the present invention by providing, in one aspect, a secondary balancer for an outboard motor vertical in-line engine which includes a crankcase, a cylinder block and a cylinder head, which are placed in this order from a front side of the engine (i.e., a hull side of a boat to which the outboard motor is mounted), a crankshaft disposed in the engine so as to extend in a substantially vertical direction, an intake pipe arranged on one side of the engine, a throttle body and an intake silencer, which are disposed on a front side of the crankcase in the engine, and a balancing device for eliminating vibration of the engine, the balancing device including a primary balancer and a secondary balancer, the second balancer comprising a pair of balancer shafts disposed in a space formed between the crankcase and the intake silencer.

According to the secondary balancer of the outboard motor-vertical engine of the structure mentioned above, it is possible to achieve miniaturization of the whole outboard motor, to obviate the need for substantial change in layout of peripherals, to unitize the secondary balancer and to improve assembling working.

Furthermore, it is possible to arrange the center of gravity of the secondary balancer in the vicinity of the center of the engine in the horizontal direction, to improve the vibration eliminating effects, to utilize the region above the secondary balancer as a space for receiving the intake silencer, thus ensuring a sufficient capacity of the intake silencer, to place the center of gravity of the engine in a lower position, thus enhancing the drivability of a boat, and to return forcedly the lubricant oil, which is collected in the balancer shaft housing, into the crankcase through an oil suction effect by the drive gears.

It is also possible to form the oil communicating passages through which the oil supply passages communicate with the main gallery for lubrication of the balancer shafts, in the cylinder block and the partition walls of the crankcase, thus permitting supply of the lubricant oil also to the secondary balancer.

Problems solved by technology

A four-stroke-cycle engine is susceptible to vibration, which is caused by a reciprocating motion of a piston of a cylinder assembly of the engine.

However, in an arrangement in which the balancer shafts are disposed separately from each other on the opposite side surfaces of the cylinder block, the distance between the balancer shafts and the crankshaft, which serves as a driving source for rotating them, is widened, thus leading to complicated structures in the layout of the balancer driving system.

Consequently, the number of the structural parts increases, resulting in the increased number of assembling steps and an increased total weight, thus being inconvenient and disadvantageous.

As a result, the cost, especially, a capital investment considerably increases.

It may be further difficult to make a change in layout of the outboard motor.

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